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                单选错位                </h1>
                <p>时间限制：10s&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;  空间限制：259MB</p>			</div>
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                                <h3>题目描述</h3><p><p><img alt="" border="0" src="../file/2134_0.jpg" /></p></p><hr/><h3>输入格式</h3><p><p>n很大，为了避免读入耗时太多，输入文件只有5个整数参数n, A, B, C, a1，由上交的程序产生数列a。下面给出pascal/C/C++的读入语句和产生序列的语句（默认从标准输入读入）： // for pascal readln(n,A,B,C,q[1]); for i:=2 to n do q[i] := (int64(q[i-1]) * A + B) mod 100000001; for i:=1 to n do q[i] := q[i] mod C + 1; // for C/C++ scanf(&quot;%d%d%d%d%d&quot;,&amp;n,&amp;A,&amp;B,&amp;C,a+1); for (int i=2;i&lt;=n;i++) a[i] = ((long long)a[i-1] * A + B) % 100000001; for (int i=1;i&lt;=n;i++) a[i] = a[i] % C + 1; 选手可以通过以上的程序语句得到n和数列a（a的元素类型是32位整数），n和a的含义见题目描述。</p></p><hr/><h3>输出格式</h3><p><p>输出一个实数，表示gx期望做对的题目个数，保留三位小数。</p></p><hr/><h3>样例输入</h3><pre>3 2 0 4 1
</pre><hr/><h3>样例输出</h3><pre>1.167
【样例说明】
a[] = {2,3,1}
正确答案	gx的答案	做对题目	出现概率
{1,1,1}	{1,1,1}	3	1/6
{1,2,1}	{1,1,2}	1	1/6
{1,3,1}	{1,1,3}	1	1/6
{2,1,1}	{1,2,1}	1	1/6
{2,2,1}	{1,2,2}	1	1/6
{2,3,1}	{1,2,3}	0	1/6
共有6种情况，每种情况出现的概率是1/6，gx期望做对(3+1+1+1+1+0)/6 = 7/6题。（相比之下，lc随机就能期望做对11/6题）
【数据范围】
对于100%的数据 2≤n≤10000000, 0≤A,B,C,a1≤100000000
</pre><hr/><h3>提示</h3><p>没有写明提示</p><hr/><h3>题目来源</h3><p>没有写明来源</p>
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